The invention is directed to a fixture in which a relatively small sample of material may be analyzed by X-ray diffraction, and more particularly to such fixtures wherein the sample is supported in alignment for analysis on an X-ray diffraction goniometer previously limited to the analysis of relatively large samples.
X-ray diffraction has become a commonly employed tool for non-destructively analyzing material for determining the chemical composition, the microstructural characteristics, and other properties of the material. If a sufficient quantity of the material to be analyzed is available, a computer coupled goniometer system may be suitably employed for the X-ray diffraction process. In such a goniometer system an X-ray beam from an X-ray generator is projected across a sample and X-ray beam diffractions emanating therefrom are picked up by a detector rotated through various incremental angles. The sample is rotated one degree for every two degrees of rotation of the detector in order to satisfy the Bragg equation for the proper analysis of the sample by X-ray diffraction. Goniometers suitable for X-ray diffraction and adaptable for use with the present invention include such systems as the commercially available system known as D-500 Diffractometer provided by Siemens-Allis, Inc., Cherry Hill, N.J.
In the analysis of a material by X-ray diffraction with known goniometers and if a sufficient quantity of the material is available, a selected portion of this material can be conventionally mounted on a glass fixture or stationed on a holder which in turn is positioned on a rotatable mount for rotation about a central axis during the exposure of the material to an X-ray beam in contact therewith. The collimated X-ray beam emanating from a fixed X-ray beam generator is directed through the material and the diffracted X-rays are detected with an electronic X-ray beam detector which is positioned radially outwardly from the sample holder and is also rotated through arc starting at an initial two theta angle of approximately 12.degree. to 15.degree., to a final two theta angle of approximately 160.degree. during the X-ray analysis. The resulting diffractogram is electronically processed in a suitable computer which provides comparisons of the derived data with diffractograms of known materials to analyze the material. This electronic analysis is very rapid and is considered to be highly accurate.
However, X-ray diffraction by using computer-coupled goniometers has not been possible in instances where only relatively small quantities of the material to be analyzed are available since the known apparatus and sample-holding fixtures utilized in such goniometers for relatively large samples cannot be used. Previously, when only relatively small samples of material were available for analysis the sample was subjected to X-ray analysis by mounting the sample in a small glass capillary and then positioning the loaded capillary in the center of a small concave receptacle. A strip of undeveloped film is placed around the sample against the walls of the receptacle and then an X-ray beam is projected through a hole in the wall of the receptacle onto the capillary to record a diffractogram of the sample on the film. The film then must be developed, analyzed and then compared to the diffractograms of known substances in order to determine the characteristics or properties of the sample. This procedure has been found to be cumbersome, time consuming, and often sufficiently inaccurate to render questionable the overall process.